Safer Sodium Storage through Carbon Coatings on Aluminum Current Collectors for Anode-less Metal Batteries

Abstract Dendrite growth and formation of an unstable solid electrolyte interphase (SEI) remain major obstacles for anode-less sodium metal batteries (SMBs). Surface modification of current collectors (CCs) is a key strategy for suppressing dendrite formation and stabilizing the SEI, leading to safer and longer-lasting SMBs. Herein, we developed a carbon-coated aluminum foil, enabling >99.9% retention in coulombic efficiency and 600 plating/stripping cycles at 2 mA cm–2. Additionally, high reversibility was demonstrated in cycling performance, even after cycling at higher current densities of up to 6 mA cm–2. A careful optimization of the coating thickness was conducted to minimize electrode volume and weight, yielding a thin (∼700 nm) and ultralight (<0.05 mg/cm2) carbon modification on Al current collectors in an anode-less configuration, while maintaining enhanced performance. The sodiophilic nature of the porous, carbon overlayer deposited by plasma-enhanced chemical vapor deposition suppresses the formation of dead sodium and stabilizes the SEI, as proven by correlative analyses using SEM, EIS, EDS, and XPS. C@Al||NVP full-cells delivered 87.8 mAh g–1 after 45 cycles at 1C and rate stability with an average capacity of 67.8 mAh g–1 at 5C. Our carbon-coated aluminum foil offers a cost-effective and abundant CC for SMBs, which suppresses the formation of sodium dendrites to enhance battery lifetime.